Sympathoadrenergic and metabolic factors are involved in ambulatory blood pressure rise in childhood obesity

We investigated in a young Italian obese population, the relationship between ambulatory BP (ABP) and several pathophysiological factors linking obesity to hypertension. A total of 89 obese children and adolescents underwent a 24-h ambulatory BP monitoring (ABPM) and an oral glucose tolerance test. The circulating levels of insulin, lipids, uric acid, C-reactive protein, interleukin-6, renin and aldosterone and the 24-h urinary levels of epinephrine, norepinephrine and albumin excretion rate were measured. Nine percent of subjects had daytime sustained hypertension (SH), 26% night-time hypertension and 11% a non-dipping pattern. SH subjects compared to those with sustained normotension (SN) were more obese (P < 0.05), with a more frequent family history of hypertension (P < 0.05), higher urinary catecholamine (P < 0.05) and heart rate values (P < 0.05) after adjustment for standard deviation score ( SDS) of body mass index (BMI) and sex. Subjects with night-time hypertension compared to those with time normotension were more obese (P < 0.0001), with a higher prevalence of impaired glucose tolerance (P < 0.05) and metabolic syndrome (P < 0.05) and higher 2h glucose (P < 0.05), uric acid (P < 0.05) and triglycerides (P < 0.05). In multivariate regression analysis, daytime systolic BP (SBP) remained independently correlated with urinary norepinephrine and SDS-BMI (P < 0.05 for both), daytime diastolic BP (DBP) with waist circumference (P < 0.05) and night-time SBP and DBP with SDS-BMI (P < 0.01 for both). The risk of having systolic and diastolic hypertension increased with the increase in SDS-BMI and waist circumference, respectively. In conclusion, in our cohort of obese children and adolescents, daytime and night-time hypertension were associated with activation of the sympathoadrenal system and worst metabolic conditions, respectively.